I've suggested this in the past. I don't think it would be a bad thing if all new users are essentially shadowbanned until a mod has approved their post or account. It would at least get rid of bots pretty effectively.
You will lose them if it takes days to approve the post. In addition with spam replies, moderating posts and approving topic will be a huge pain for the moderators. Now if some of the newbies post get approved with delay the chance of losing them is high. I'm sharing my personal experience based on facebook group. Can you share link of that discussion?